import java.util.Scanner;//1303: 【入门】冷饮的价格（1）

public class Main1303 {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        double n = sc.nextDouble();
        if (n >= 10 && n > 0 && n <= 100) {
            System.out.println(n * 2);
        } else {
            System.out.println(n*2.2);
        }
    }
}
